When restoring the old tube equipment (tube receivers ) does it make any
difference if the old paper capacitors are replaced with the ceramic
disk or should another type be used ?

You are better off replacing them with plastic film capacitors, because
many of them are going to be of larger values where C0G ceramic disc capacitors
that can handle the voltage will be expensive and rare.

For smaller ones, such as in an IF strip, you would be fine replacing them
with C0G ceramics.

You don't want to be using high density ceramics.
I know for RF one needs to use capacitors that are rated for rf but in
the audio stages does it really matter what kind of capacitor is used as
long as it is the correct value ?

It does, because it has to fit and be stable and not fail. And in the case
of high density ceramics like Z3U types, they are very nonlinear which is
okay for supply decoupling but bad news for IF strips.
Reason for asking is that I bought an old receiver that someone has
replaced many of the capacitors. The book says pape capacitors for some
but they have been replaced by the ceramic disk type.

When was it done? If it was done sixty years ago, likely ceramics were the
only alternative you could get. And back then, high voltage NP0s were
available at your local tv repair supplier.
--scott

When restoring the old tube equipment (tube receivers ) does it make any
difference if the old paper capacitors are replaced with the ceramic
disk or should another type be used ?

I know for RF one needs to use capacitors that are rated for rf but in
the audio stages does it really matter what kind of capacitor is used as
long as it is the correct value ?

Reason for asking is that I bought an old receiver that someone has
replaced many of the capacitors. The book says pape capacitors for some
but they have been replaced by the ceramic disk type.

Paper capacitors were never that good, just what was available. They can
pick up noise (which is why they are often marked so you know which side
should go to ground), they are inductive, they are big. But that's all
there were until better capacitors came along.

It's no different from electrolytics, I can't think of any application
where a polarized capacitor is needed. But in order to get higher
capacitance, in a reasonable size package, electrolytics (and
tantalum) make them practical. But it confuses people, they see the
polarization and think that's the needed factor.

So paper capacitors were used, and there's absolutely no reason (unless
someone is finicky with making everything "original") to use them still,
if you could get them. And a lot of old equipment suffers, paper
capacitors gone bad because they had a life span.

I came along after ceramic capacitors became viable in values useful for
RF bypascc capacitors, so that's what I'd use, but others seme to want
something newer. They won't have the inductance of paper capacitors,
otehr than long leads. Recapping decades ago would see paper capacitors
replaced with ceramic.

On Wed, 10 Oct 2018 15:02:53 -0400, Ralph Mowery wrote:
When restoring the old tube equipment (tube receivers ) does it make any
difference if the old paper capacitors are replaced with the ceramic
disk or should another type be used ?

I know for RF one needs to use capacitors that are rated for rf but in
the audio stages does it really matter what kind of capacitor is used as
long as it is the correct value ?

Reason for asking is that I bought an old receiver that someone has
replaced many of the capacitors. The book says pape capacitors for some
but they have been replaced by the ceramic disk type.

This topic takes me back. One of my first "real" radio repairs was back in High School electronics class on another student's old Philco cathedral radio. Not one of the fancy, classic cathedrals but a lower end one, maybe a 5 tuber. Still, a cool old radio.

The radio was nearly dead, no audio, just a minor hum from the speaker. I used the shop's signal tracer and I could get audio at the IF stage but no audio at the volume control. Long story short, the coupling cap had opened up. The first suitable cap I could find was a disk ceramic and I subbed that for the opened up cap in the bathtub. It worked!

The other guy was real happy about the repair. I thought the audio wasn't great but I didn't know much about old radios except old radios on TV or in the Movies always sounded crappy. But now I figure the ceramic coupling cap may have worsened the sound.

As I've since learned, there's two kinds of ceramic caps. The first kind are very stable but are bulky for their capacitance and voltage rating. They are normally used in such things as tuned circuits.

The second type of ceramic cap is compact but they show high changes in capacitance with temperature, frequency and applied voltage. They are fine for bypass and coupling as long as the cap's limitations are taken into consideration. I'm sure the ceramic cap I used was the second type. The changes in capacitance with voltage can cause audible audio distortion which won't happen with other types of caps. Here's an article which goes into the non linerarities of various types of caps without delving into audiophile metaphysics:

But if you're OK with the sound of your radio, stay happy. Most of this audiophile stuff is lost on the 99,9% of us who lack the superpower to tell the difference between the characteristic sound of a paper in oil cap and a polyester cap.

But if you're OK with the sound of your radio, stay happy. Most of this audiophile stuff is lost on the 99,9% of us who lack the superpower to tell the difference between the characteristic sound of a paper in oil cap and a polyester cap.

That explains a lot to me. I had never given a thought as to a
capacitor at audio. I doubt I could tell any difference in the sound,
but if I ever pull the old receiver back out I may replace the replaced
capacitors with some of the 'orange drop' type.

I well aware of the audiophile 'snake oil'. The best one is a line cord
that goes for over $ 100. Guess they do not think of the regular copper
wire going from the socket to the breaker box, or cheap wire going back
to the power generating station.

NP0/C0G dielectrics are pretty good, but many of the other dielectrics have
a lot of distortion. The good news is that the large DC bias on them makes
it less of an issue, but they were cheap and plentiful.
That explains a lot to me. I had never given a thought as to a
capacitor at audio. I doubt I could tell any difference in the sound,
but if I ever pull the old receiver back out I may replace the replaced
capacitors with some of the 'orange drop' type.

A decade ago I'd have recommended doing that, but I don't think you can
buy Sprague Orange Drops anymore. They were the standard replacement types
for those applications for many many years. Now, I guess I would suggest
the Panasonic sputtered mylars from digi-key, or the xicon sputtered mylars.
I well aware of the audiophile 'snake oil'. The best one is a line cord
that goes for over $ 100. Guess they do not think of the regular copper
wire going from the socket to the breaker box, or cheap wire going back
to the power generating station.

There is a lot of silliness in the audiophile market, and a lot of gear
that is designed to be distorting in an interesting way.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

I don't use ceramic caps in audio applications but I'm not sure I'd hear
the difference. It's just a matter of "good practice" for me. The old
Philco didn't sound perfect but it didn't sound really bad either. It
was 40 years old at the time and the fact that it then worked pretty well
was good enough for everyone involved.

I think any plastic film cap that has a suitable capacitance and meets or
exceeds the original's voltage rating would be fine. I have some old
paper caps but I'll never use them. Maybe I'll give them to some guitar
amp guy.

I have been working and collecting electronic parts for over 50 years so
have a fair stock for someone that is just in for the hobby and does not
work on them for a living. I just have never gotten into using other
than similar parts for replacment other than electrolytics for the old
oil filled capacitors and tublar ones for the old paper type. I can
work with the older tube equipment, but have not done very much of it as
transistors were in use by the time I really got into electronics. I
just started a Boat Anchor station back in July when I picked up a
Johnson Viking transmitter for $ 40. Now I have about $ 400 invested in
the AM station. It is from about the time I was born.

Sort of thinking about putting together a setup from aroung 1970 or so
using tube equipment. That would have been around the time I got my ham
license. Just out of room now in the ham shack.

On Sun, 21 Oct 2018 13:39:58 -0400, Scott Dorsey wrote:
A decade ago I'd have recommended doing that, but I don't think you can
buy Sprague Orange Drops anymore. They were the standard replacement
types for those applications for many many years. Now, I guess I would
suggest the Panasonic sputtered mylars from digi-key, or the xicon
sputtered mylars.

Antique Electronic Supply is still selling Orange Drops but they're being
made by someone else now. Vishay? CDE? I'm not sure. But they're
supposed to be the same as Sprague Orange drops.

Those Chinese yellow capacitors seem to be clones of the old Sprague
yellow jackets. I've used them and they've worked fine for me, although
some other people report problems. I did catch a leaker when I was
testing a batch a few years ago.

I've never had a problem with the brown Panasonics from Digi-Key and they
would be my go-to cap if wanted some brand name confidence.